Kemp has shown improvement recently, and is getting closer to game action. Kemp has been limited by an ankle injury during spring. He hit .270/.328/.395 in 263 at-bats last year.
"He brings a different element," said Antony, who noted Mastroianni is a big stolen-base threat.
Diaz is expected to be in camp Monday. Diaz was pursued by a number of teams during the offseason, but ultimately chose St. Louis.
Portillo was designated for assignment by the club in December, but cleared waivers and remained with the team. He struggled with injuries for much of the 2013 season.
"That’s the estimate we’re looking at," assistant general manager Thad Levine said. "There are things we want to see him do first, which is making those out-of-the-ordinary plays."
"I don’t really know," Duquette said of if he had a sense Santana would sign somewhere in the next day or two, per MLB.com. "I really don’t. I really don’t know what’s real and what’s not real in that case."